Baltic Birch Density
Finland and Russia both export Baltic birch to the U.S. in the form of high-density plywood (HDP). Baltic birch HDP made in the U.S. is considered to be of lesser quality. Maple is also made into HDP, but Baltic birch is commonly preferred. Baltic birch HDP has a fine grain and does not have holes or gaps between the layers. Its high density means that it weighs less than other forms of plywood.
David Kriege and Richard Berry, in their book “The Dobsonian Telescope: A Practical Manual for Building Large Aperture Telescopes,” report that a sheet of Baltic birch HDP plywood that is 3/4 inch thick and has 13 plies has a density of .026 pounds per cubic inch. Ross Sacket, writing in the Amateur Telescope Makers forum, writes that he tested the density of six panels of Russian-made HDP ranging from 1/8 to 3/4 inch thick. He reported a density range from .022 to .024 pounds per cubic inch. He found that the average density was .0234 pounds per cubic inch. Sacket expected the thinner sheets to be more dense because of they contained more glue, but he found that was not true.
Baltic birch HDP plywood is usually sold in 5-feet-wide square sheets. There are usually seven to nine thin plies in a 1/2-inch-thick sheet. Most forms of plywood are sold in sheets that are 4 feet wide and 8 feet long.
Finnish Baltic birch HDP is said to be the highest quality, followed by Russian birch. Baltic birch is less prone to damage by insects and disease. The surface of Finnish HDP is virtually free of football-shaped patches and plugs often found plywood.
The fine, flat surface of Baltic birch HDP is easy to paint; it easily accepts nails, screws and staples. There may be some splintering at the edges of a machined cut.
Baltic birch HDP is popularly used for making architectural models, doll houses and other forms of miniature buildings where a thin, strong plywood is required. Both sides of Baltic birch HDP can be used for the exterior and interiors of models.